Heated ceramic injector

Abstract

An inductively coupled plasma (ICP) ion source assembly is described. In various embodiments, the ICP ion source assembly comprised a ceramic injector with an outlet opening diameter less than about 0.8 mm and positioned such that when a plasma is maintained in the ICP ion source the outlet is in contact with the plasma.

Description

4637-0022WO01HEATED CERAMIC INJECTORRELATED APPLICATIONS

[0001] This application claims the benefit of, and priority to, U.S. Provisional Application No. 63 / 750,154, filed January 27, 2025, entitled “Heated Ceramic Injector,” the contents of which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to ion sources and, particularly, to novel injectors for use with inductively coupled plasma (TCP) ion generation for mass cytometry (ICP-MS).BACKGROUND

[0003] ICP mass cytometry instruments, such as for example the Standard BioTools CyTOF® XT™ system, conduct mass cytometric analysis by labeling cells (typically with heavy metals, and often with one or isotopes thereof), nebulizing the cells for introduction into the ICP plasma which atomizes the cells and ionizes the labels (e.g. the heavy metal labels) and then generates a mass spectrum of the ionized labels. However, several difficulties and sources for error can arise in this process.

[0004] One difficulty and source for error associated with mass cytometry is that cells are introduced via nebulization and their arrival to the ICP plasma is random which results in cell-cell fusion events, that is, more than one cell enters the plasma at the same time creating what is called a multiplet event. The signals from these multiplet events are thrown out during analysis, as the single cell information is lost. To minimize the occurrence of multiplet events, users are instructed to keep the sample concentration low. However, while such low sample concentrations decrease the occurrence of multiplet events, they also decrease sample throughput and increase the time required to obtain sufficient data as fewer cells per unit time enter the ICP plasma for atomization / ionization and subsequent analysis.

[0005] In addition, higher sample concentrations (typically measured in million of cells per milliliter, M / mL) can cause clogging of the injector used to introduce the nebulized sample into the ICP region. Accordingly, there is a need for instruments and methods for increased4637-0022WO01sample throughput without the concomitant increase in multiplet events and injector clogging.SUMMARY

[0006] In various aspects and embodiments, provided are ICP ion source assemblies and methods for ICP mass cytometry that: (a) reduce the incidence of multiplet events, (b) improve sample throughput, and / or (c) decrease the incidence of injector clogging.

[0007] In various aspects and embodiments, provided are ICP ion source assemblies comprising: (a) an envelope surrounding a plasma zone, (b) a coil disposed around at least a portion of the envelope and configured to generate a RF electromagnetic field within the plasma zone to generate and / or maintain a plasma in the plasma zone, (c) a conduit extending into the envelope and having a first end adjacent the plasma zone, and (d) a ceramic injector positioned within then conduit, where the ceramic injector has an outlet having opening with an opening diameter between about 0,4 mm and about 0.8 mm, and a lumen in fluidic communication with the outlet, the lumen having a diameter greater than that of the outlet opening diameter, and (d) where the outlet of the ceramic injector extends past the first end of the conduit and into the plasma zone such that when the plasma is maintained in the plasma zone the outlet is in contact with the plasma.

[0008] In various aspects and embodiments, provided are ICP ion source assemblies for mass cytometry comprising: (a) an envelope surrounding a plasma zone, (b) a conduit extending into the envelope and having a first end adjacent the plasma zone, and (c) a ceramic injector positioned within then conduit, where the ceramic injector has an outlet that extends past the first end of the conduit and into in the plasma zone such that when the plasma is maintained in the plasma zone the outlet is in contact with the plasma, and where the ceramic injector is configured such that it can operate substantially continuously with a sample cell concentration of about 2 M / mL or greater for more than about 15 hours without a substantial decrease in single cell events per second.

[0009] In various embodiments, the ceramic injector is positioned such that the outlet, also referred to as the tip, reaches a temperature of at least 350 °C, at least 400 °C, at least 500 °C, and / or at least 600 °C during ion source operation to ionize samples. In various4637-0022WO01embodiments, the ceramic injector is positioned such that the outlet reaches a temperature between about 350 °C and about 600 °C during ion source operation to ionize samples.0010] It is to be understood that the ceramic injector is heated by positioning the ceramic injector outlet such that it is in contact with the plasma in the plasma zone. A separate heating element is not required.

[0011] In various embodiments, the ceramic injector lumen has a diameter between about 1 mm and about 10 mm. In various embodiments, the transition from the lumen diameter to the outlet opening diameter is direct, that is for example, the transition from the lumen diameter to the outlet opening diameter describes a truncated cone with one end of the cone coterminous with the outlet opening. In various embodiments, the truncated cone has a tapering angle α (as measured interior of the injector) between about 5 and about 180 degrees, between about 10 and about 100, and / or between about 20 and about 90 degrees. In various embodiments, the transition from the lumen diameter to the outlet opening diameter describes a truncated cone with one end of the cone coterminous with the outlet opening and the transition occurs over an axial distance between about 5 mm to about 10 mm, and / or between about 4 mm to about 8 mm.

[0012] In various embodiments, the ceramic injector has a length in a range between about 5 mm to about 50 mm. In various embodiments, the envelope has an inner diameter in a range between about 5 mm to about 30 mm.

[0013] It is to be understood that at least a portion of the ions generated by the ICP ion source pass through an orifice in a sampler for subsequent analysis by a downstream instrument, such as, e.g., mass analysis by a mass spectrometer. In various embodiments, an axial distance between the outlet of the ceramic injector and the sampler orifice can be equal to or less than about 2 inner diameters of the envelope, e.g., in a range between about 5 mm to about 60 mm. In various embodiments, the axial distance between the outlet of the injector and the sampler orifice is in the range between about 5 mm to about 60 mm, between about 10 mm to about 50 mm, and / or between about 20 mm to about 40 mm.4637-0022WO01

[0014] It is to be understood that the ICP ion source assemblies and methods for ICP mass cytometry provided herein make use of a ceramic injector instead of, for example, a quartz glass or metal injector. Suitable ceramic injector materials include, but are not limited to aluminum nitride, aluminum oxynitride, aluminum oxide, alumina, silicon nitride, and sialon.

[0015] The envelope can have a variety of different profiles (shapes). By way of example, the envelope can have a substantially cylindrical shape. In various embodiments, the envelope can have a varying cross-sectional dimension in a plane orthogonal to its longitudinal axis. By way of example, the envelope, can be in the form of a truncated cone, a trumpet-like shape, or any other suitable shape, including a shape formed by revolving a profile, a parabola, around an axis of symmetry.

[0016] The envelope can be formed of an electrically non-conductive material with a melting point of at least about 300 °C. By way of example, and without limitation, the envelope can be formed from any of a ceramic (e.g., aluminum nitride, aluminum oxynitride, alumina, silicon nitride, sialon), glass, fused silica and sapphire.

[0017] It is to be understood that samples delivered by the ceramic injector to the ICP plasma are entrained in an injector gas, provided by an injector gas supply. The injector gas enters the injector via an inlet in fluid communication with the lumen.

[0018] In various embodiments, the envelope and conduit are substantially tubular. In various embodiments, a gap exists between inner surface of the conduit and outer surface of the ceramic injector so as to define an auxiliary inlet for delivering an auxiliary gas to a region between an outer surface of the injector and an inner surface of the conduit. In various embodiments, a gap between the outer surface of the conduit and inner surface of the envelope defines a vortex inlet for delivering a vortex gas to a region between an outer surface of the conduit and an inner surface of the envelope. The ICP ion source assembly can include an auxiliary gas supply and a vortex gas supply for supplying the auxiliary gas and the vortex gas to the assembly.

[0019] In various embodiments, the injector gas, the auxiliary gas and the vortex gas can be the same gas, e.g., supplied via a single gas supply. In other embodiments, at least two of the injector gas, the auxiliary gas and the vortex gas can be different gases. A gas manifold can4637-0022WO01be configured to receive the gas from the single gas supply and distribute portions of the received gas as the injector, the auxiliary and the vortex gas.0020] In various embodiments, the coil comprises at least one RF coil disposed at least partially around the envelope.

[0021] In various embodiments, the at least one RF’ coil can comprise two or more RF coils that are electrically connected in parallel. In various embodiments, the at least one RF coil can comprise two or more RF coils that are electrically connected in series. In various embodiments, the at least one RF coil has a split-coil structure having two or more segments that are mechanically coupled to one another so as to surround the torch envelope and are electrically coupled to provide an electrically conductive path between the two or more segments. In various embodiments, each of the coil segments can have a substantially semi¬ circular profile. In some such cases, the two segments can be mechanically coupled to fully surround the torch envelope.

[0022] In various embodiments, the at least one RF coil can be axially separated from the sampler orifice by a distance equal to or less than about 1 / 2 of diameter of the coil.

[0023] In various embodiments, the ICP ion source assembly can include a radiofrequency (RF) source in electrical communication with the RF coil for generating an RF field within at least a portion of the plasma zone for igniting the plasma. The RF source can be configured to apply an RF voltage at a frequency in a range of about 900 kHz to about 10 GHz to the RF coil, In various embodiments, the RF source is configured to apply an RF voltage in a range of about 25 MHz to about 50MHz to the RF coil. By way of example, the RF voltage can have an amplitude in a range of about 50 V to about 6 kV.

[0024] The ICP ion source assembly can be enclosed in a housing. The housing can be formed of a metal, such as aluminum, copper, stainless steel, or metal plated plastic or metal plated ceramic. The thickness of the walls of the housing can be selected so as to protect the assembly from electromagnetic interference (EMI). Further, the housing can include one or more cooling channels for receiving a coolant.

[0025] As used herein, the abbreviation “M / mL” when used in the context of a concentration of cells in sample means to millions of cells per milliliter.4637-0022WO01

[0026] Further understanding of various aspects of the embodiments may be obtained by reference to the following detailed description in conjunction with the associated drawings, which are described briefly below.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings are not necessarily to scale or exhaustive. Instead, emphasis is generally placed upon illustrating the principles of the embodiments described herein. The accompanying drawings, which are incorporated in this specification and constitute a part of it, illustrate several embodiments consistent with the disclosure. Together with the description, the drawings serve to explain the principles of the disclosure.

[0028] In the drawings:

[0029] FIG. 1 A shows an example of an ICP ion source assembly according to various embodiments,

[0030] FIG. 2A shows a cross-sectional cut through of a ceramic injector according to various embodiments, illustrating the transition from the lumen diameter to the outlet opening diameter,

[0031] FIG. 2B shows a cross-sectional cut through illustrating the transition from a lumen diameter to the outlet opening diameter of a prior art injector,

[0032] FIGS. 3A and 38 are pictures of the ICP ion source region in operation, where FIG.2A shows a prior art injector configuration and FIG. 28 a ceramic injector configuration in accord with various embodiments of the ICP ion source assemblies provided herein,

[0033] FIG. 4 shows data on the temperature of the ceramic injector outlet at various axial positions,

[0034] FIG. 5 shows data on multiplet events for various sample concentrations, comparing various embodiments of the present inventions to prior methods,4637-0022WO01

[0035] FIG. 6 shows data on cell recovery (singlet event recovery and Iridium ion (Ir+) recovery), comparing various embodiments of the present inventions to prior methods,

[0036] FIG. 7 shows data acquisition speed (singlet events per second), comparing various embodiments of the present inventions to prior methods, and

[0037] FIG. 8 shows data on the inability of a prior art ICP ion source assembly to operate for a sustainable time with the higher sample throughput concentrations (M / mL) usable according to various embodiments of the present invention.DETAILED DESCRIPTION

[0038] It will be appreciated that for clarity, the following discussion will explicate various aspects of embodiments of the applicant’s teachings, while omitting certain specific details wherever convenient or appropriate to do so. For example, discussion of like or analogous features in alternative embodiments may be somewhat abbreviated. Well-known ideas or concepts may also for brevity not be discussed in any great detail. The skilled person will recognize that various embodiments of the applicant’s teachings may not require certain of the specifically described details in every implementation, which are set forth herein only to provide a thorough understanding of the embodiments. Similarly, it will be apparent that the described embodiments may be susceptible to alteration or variation according to common general knowledge without departing from the scope of the disclosure. The following detailed description of embodiments is not to be regarded as limiting the scope of the applicant’s teachings in any manner.

[0039] The following detailed description refers to the accompanying drawings. The same or similar reference numbers may have been used in the drawings or in the description to refer to the same or similar parts. Also, similarly named elements may perform similar functions and may be similarly designed, unless specified otherwise. Details are set forth to provide an understanding of the exemplary embodiments. Embodiments, e.g., alternative embodiments, may be practiced without some of these details. In other instances, well known techniques, procedures, and components have not been described in detail to avoid obscuring the described embodiments.4637-0022WO01

[0040] Various terms are used herein in accordance with their ordinary meanings in the art. The terms “plasma gas flow” and “vortex gas flow” are used herein interchangeably to refer to a gas introduced into an envelope about a plasma zone through an inlet other than the inlet of an injector, which is in utilized to introduce a gas and a sample into the plasma zone. A “vortex gas flow” may or may not include any vortices as it flows through the plasma torch. The term “axial distance,” as used herein, refers to a distance between two components / elements of the ICP ion source assembly along a longitudinal axis thereof.

[0041] As used herein the term “and / or” includes any and all combinations of one or more of the associated listed items,

[0042] The various aspects and embodiments described herein make use of a ceramic injector and position the injector such that the outlet of the injector is in contact with the plasma formed in the plasma zone of the ICP ion source. Various embodiments in this manner thus provide for a heated ceramic injector when the ICP ion source is in use without the need for a separate heater element to heat the ceramic injector,

[0043] It has been unexpectedly discovered that despite drawbacks that can arise from contacting the plasma with the injector, various benefits can be obtained in various aspects and embodiments provided herein, including but not limited to: (a) the reduction of the incidence of multiplet events, (b) increased sample throughput, and / or (c) decreased incidence of injector clogging.

[0044] Referring to FIG. 1, an ICP ion source assembly 100, according to various embodiments, comprises an envelope 102 surrounding and at least partially enclosing a plasma zone 104, the region in which the coil 106 (an RF coil with three turns is illustrated) generates and / or maintains the plasma 108 that ionizes samples (e.g. heavy metal labeled cells) introduced thereto via the outlet 116 of the ceramic injector 112. The outlet 116 of the ceramic injector 112 is positioned such that it extends past a first end 112 of the conduit 110 and into the plasma zone such that when the plasma 108 is maintained in the plasma zone the outlet 116 is in contact with the plasma 108.4637-0022WO01

[0045] The ceramic injector 114 further comprises a lumen 118 that is in fluidic communication with the outlet 116 and an inlet 120 to the ceramic injector though which samples and injector gas are provided. It is to be understood that other gas flows can also be, and often are, provided such as for example an auxiliary gas and / or vortex gas. In various embodiments, a gap exists between inner surface of the conduit 110 and outer surface of the ceramic injector 114 so as to define an auxiliary inlet for delivering an auxiliary gas to the region between an outer surface of the injector and an inner surface of the conduit. In various embodiments, a gap between the outer surface of the conduit 110 and inner surface of the envelope 102 defines a vortex inlet for delivering a vortex gas to a region between an outer surface of the conduit 110 and an inner surface of the envelope 102.

[0046] In typical mass cytometry operation, ions generated by the ICP ion source assembly 100 pass through an orifice 130 in a sampler 132 for subsequent mass analysis. In various embodiments, an axial distance between the outlet 116 of the ceramic injector 114 and the sampler orifice 130 is equal to or less than about 2 inner diameters of the envelope 102. In various embodiments, the axial distance between the outlet of the injector 116 and the sampler orifice 130 is in the range between about 5 mm to about 60 mm, between about 10 mm to about 50 mm, and / or between about 20 mm to about 40 mm.

[0047] It has been discovered that the dimensions and geometry of the passage through and exit from the ceramic injector are important to obtain the various benefits observed with the various aspects and embodiments of the present inventions. In various embodiments, the outlet 116 of the ceramic injector 114 has an outlet opening diameter between about 0.4 mm and about 1 mm, and the injector lumen 118 has a diameter greater than that of the injector outlet opening. In various embodiments, the lumen diameter is between about 1 mm and about 10 mm, In various embodiments, the lumen diameter is between about 1 mm and about 5 mm.

[0048] In addition to the diameters of the lumen and ceramic injector outlet, in various embodiments the transition from the lumen diameter to the outlet diameter provides for various benefits, such as, for example, reducing the likelihood of injector outlet clogging at sample concentrations above about 1 M / mL in mass cytometry. Referring to FIGs. 2A and 2B, in various embodiments, the ceramic injector 214 lumen 218 transitions from the lumen4637-0022WO01diameter to the outlet opening 216 diameter in a direct manner, as compared to, for example, to the transition shown in FIG. 2B, where the lumen 258 diameter transitions to the outlet 256 diameter before 257 reaching the outlet 256, As illustrated in FIG. 2A, in various embodiments, the transition from the lumen diameter 220 to the outlet opening 216 diameter describes a truncated cone with one end of the cone coterminous with the outlet opening 216. In various embodiments, the truncated cone has a tapering angle α 222 between about 5° and about 180°, degrees, between about 10° and about 100°, and / or between about 20° and about 90°, degrees. In various embodiments, the transition from the lumen diameter 220 to the outlet opening 216 diameter describes a truncated cone with one end of the cone coterminous with the outlet opening and the transition occurs over an axial distance d 224 between the range of about 4 mm to about 8 mm and / or about 5 mm to about 10 mm.0049] While FIG. 1A schematically illustrates the position of a ceramic injector outlet with respect to a plasma, FIGS. 3A and 3B are photographs showing the spatial relation of the plasma 508, 558 to the outlet 516, 566 of the injector 514, 564, where FIG. 3A is a photograph of a convectional injector position with a gap 570 between the injector outlet 566 and plasma 558, and FIG. 3B shows an configuration according to various embodiments of the present inventions where the injector outlet 516 is in contact with, and even extends into the plasma 508. It should be noted that in FIG. 3B, one of the three RF coil 506 rings is blocking the camera view of the injector outlet. It should also be noted that in FIGS. 3 A and 3B, the plasma 508, 558 is the bright white region and extends from about the RF coil 506, 556 ring closest to the respective injector outlet 516, 566 to the respective sampler orifice 530, 580. The envelope 502, 552 end can also be discerned in these photos.

[0050] Example 1: Ceramic Injector Outlet Temperature

[0051] The data of this example was obtained with a modified Standard BioTools CyTOF® XT™ mass cytometer instrument (Standard BioTools, Inc., 2 Tower Place, Suite 2000, South San Francisco, CA, USA 94080) using an alumina ceramic injector having an outlet diameter of 0.7 mm, and a lumen diameter of 4 mm, that directly tapered (see, e.g., FIG. 2A) to the outlet diameter over an axial distance of about 6 mm. The effect of injector position relative to the plasma was studied by moving the injector in the axial direction towards the plasma (i.e. in the direction of the sampler orifice, see for example FIGS.3A, 3B) in 1 mm4637-0022WO01increments. The temperature of the injector outlet (y-axis) as a function of displacement from its conventional position in the CyTOF XT (x-axis) is shown in FIG.4. The starting position, 0 displacement corresponds to the unmodified instrument. The outlet, or tip, temperature can be seen to rise significantly as it approaches the plasma, and is believed to substantially come into contact with the plasma at a displacement between about 3 mm and 6 mm.

[0052] Example 2: Comparison to a Conventional Injector Configuration

[0053] This example compares various performance and other characteristics of a conventional ICP ion source assembly, and one according to various embodiments of the present inventions. The conventional ICP ion source assembly data of this example was obtained with Standard BioTools CyTOF XT mass cytometer instruments, and a modified CyTOF XT mass cytometer instruments modified in accord with various embodiments of the present inventions. The unmodified instrument will be referred hereafter, and in Example 3, simply as the “XT,” and the instrument modified in accord with various embodiments of the present teachings will be refereed hereafter simply as the “XT Pro.”

[0054] The XT studies employed a quartz injector having an outlet diameter of 1.5 mm, and a lumen diameter of 4 mm. The sample employed was peripheral blood mononuclear cells (PBMC) labeled with iridium. The instrument was operated with a sample concentration of IM / mL, unless noted otherwise. FIG. 3A illustrates the position of the injector outlet relative to the plasma in this study.

[0055] The XT Pro studies employed an alumina ceramic injector as described in Example 1, with the injector outlet positioned 5mm closer to the sampler orifice (e.g. at position +5 in FIG. 4) and in contact with the plasma. FIG.3B illustrates the position of the ceramic injector outlet relative to the plasma in this study. The sample employed was peripheral blood mononuclear cells (PBMC) labeled with iridium. The instrument was operated with a sample concentrations of 2M / mL and 5 M / mL, unless noted otherwise.4637-0022WO01

[0056] Referring to FIG. 5, data for the XT is represented by the unfilled symbols, and for the XT Pro by the filled symbols. The data presented is for a range of PBMC cell concentrations (x-axis), and shows the percentage of cells “lost” due to multiplet events, and thus data that must be discarded, (y-axis) as a function of sample concentration (x-axis). It can be seen that the ICP ion source assembly according to various embodiments of the present inventions (the XT Pro), shows a significant decrease in multiplet events across all sample concentrations compared to a conventional ICP ion source assembly (the XT data).

[0057] Referring to FIG. 6, the data is from 3 replicates performed for each condition (XT, IM / mL; XT Pro, 2M / mL; XT Pro, 5M / mL) on 3 different instruments for each injector configuration, for a total of 9 replicates per condition. Shown is the observed cell recovery for the XT (leftmost set of bars) compared to the XT Pro (two sets of bars to the right).Recovery' of the Ir+ is shown by the dark-colored bars, and of the single cells by the light¬ colored bars, where the error bars represent 1 standard deviation (1 sigma). FIG. 6 shows substantially equivalent single cell recovery between the XT (conventional design) at 1 M / nL sample concentration and the XT Pro at 2 M / mL concentration. When the concentration is increased to 5 M / mL with the XT Pro, the single cell recovery drops by -10%. However, the data acquisition rate for the XT Pro is substantially greater than that observed for the XT. This is shown by the measured events / sec data above each set of bars, where the error (+ / -) represents 1 standard deviation (1 sigma). This sho ws that various embodiments of the present inventions allow for almost double the throughput (compare 284 ±17 events / sec for the XT at IM / mL to 589 ±56 events / sec for XT Pro as 2M / mL) without any compromises to cell recovery, and over four times the throughput with a -10% drop in cell recovery.

[0058] Referring to FIG. 7, the improvement in data acquisition speed achieved with the XT Pro is more clearly seen, plotting singlet rate (events) per second (y-axis) as a function of data acquisition time (x-axis) over a 24 hour period. The bottom series of data points 702 is for the XT with a 1 M / mL sample concentration, the middle series of points 704 is for the XT Pro with a 2 M / mL sample concentration, and the upper series of points 706 is for the XT Pro with a 5 M / mL sample concentration. As will be illustrated further with reference to FIG.8A, the XT Pro (i.e. a ICP ion source assembly in accord with various embodiments of the present inventions) data shows the ceramic injector remains free of buildup (i.e., clogging) even after running the instrument for 24 hours with such high sample concentrations.4637-0022WO01

[0059] Example 3: Quartz; Injector Clogging

[0060] In this example, an XT using a quartz injector having an outlet diameter of 0.7 mm, and a lumen diameter of 4mm was used, see FIG. 3A for an illustration of the position of the injector outlet relative to the plasma in this study. The sample employed was peripheral blood mononuclear cells (PBMC) labeled with iridium. The instrument was operated with a sample concentration of 5 M / mL.

[0061] Referring to FIGS. 8A and 8B, data is shown as a function of acquisition time (x- axis) for the singlet rate (events) per second (dashed curve and left y-axis), and MUG pressure (solid curve and right y-axis). As can be seen in FIG. 8A, after about 12 hours of acquisition, the signal (singlet rate / sec) begins to drop and plummets after about 15 hours, while concomitantly the MUG pressure begins to rise after about 12 hours, and exponentially rises after about 15 hours, both behaviors indicative of build-up (clogging) of the injector at the tip. Referring to FIG. 8B, upon removal and inspection, the injector outlet can be seen to be completely blocked (discoloration) and unusable.

[0062] The specific details of particular embodiments may be combined in any suitable manner without departing from the spirit and scope of embodiments of the invention.However, other embodiments of the invention may be directed to specific embodiments relating to each individual aspect, or specific combinations of these individual aspects

[0063] The above description of example embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above,

[0064] In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.

[0065] Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes4637-0022WO01and elements have not been described in order to avoid unnecessarily obscuring the present invention. Additionally, details of any specific embodiment may not always be present in variations of that embodiment or may be added to other embodiments.

[0066] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

[0067] As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a method” includes a plurality of such methods and reference to “the sample” includes reference to one or more samples and equivalents thereof known to those skilled in the art, and so forth. The invention has now been described in detail for the purposes of clarity and understanding. However, it will be appreciated that certain changes and modifications may be practice within the scope of the appended claims.

[0068] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes. None is admitted to be prior art.

Claims

4637-0022WO01WHAT IS CLAIMED IS:

1. An inductively coupled plasma (ICP) ion source assembly (100), comprising:an envelope (102) surrounding a plasma zone (104),a coil (106) disposed around at least a portion of the envelope and configured to generate a RF electromagnetic field within the plasma zone to generate and / or maintain a plasma (108) in the plasma zone,a conduit (110) extending into the envelope and having a first end (112) adjacent the plasma zone, anda ceramic injector (114) positioned within the conduit, the ceramic injector having:an outlet having opening (116) with an opening diameter between about 0.4 mm and about 0.8 mm, anda lumen (118) in fluidic communication with the outlet, the lumen having a diameter greater than the outlet opening diameter,wherein outlet of the ceramic injector extends past the first end of the conduit and into the plasma zone such that when the plasma (108) is maintained in the plasma zone the outlet is in contact with the plasma.

2. The ICP ion source assembly of Claim 1, where in the lumen diameter is between about 1mm and about 10 mm.

3. The ICP ion source assembly of Claim 1, wherein the lumen diameter directly transitions to the outlet opening diameter at the outlet opening.

4. The ICP ion source assembly of Claim 3, wherein the transition from the lumen diameter to the outlet opening diameter describes a truncated cone with one end of the cone coterminous with the outlet opening.

5. The ICP ion source assembly of Claim 4, wherein the truncated cone has a tapering angle a between about 5 and about 180.4637-0022WO016. The ICP ion source assembly of Claim 4, wherein the truncated cone has a tapering angle a between about 10 and about 100.

7. The ICP ion source assembly of Claim 4, wherein the truncated cone has a tapering angle a between about 20 and about 90.

8. The ICP ion source assembly of Claim 4, the transition occurs over an axial distance between the range of about 4 mm to about 8 mm.

9. The ICP ion source assembly of Claim 4, the transition occurs over an axial distance between the range of about 9 mm to about 11 mm.

10. The ICP ion source assembly of Claim 1, wherein the coil comprises an RF coil.

11. The ICP ion source assembly of Claim 10, wherein the RF coil comprises two or more RF coils electrically connected in series.

12. The ICP ion source assembly of Claim 1, wherein the ceramic injector comprises a ceramic composed of one or more of aluminum nitride, aluminum oxynitride, aluminum oxide, alumina, silicon nitride, and sialon.

13. The ICP ion source assembly of Claim 1, wherein the ceramic injector has a length in a range between about 5 mm to about 50 mm.

14. The ICP ion source assembly of Claim 1, wherein the envelope has an inner diameter in a range between about 5 mm to about 30 mm.

15. The ICP ion source assembly of Claim 1, wherein the envelope has a substantially cylindrical shape.

16. The ICP ion source assembly of Claim 1, wherein the envelope comprises a non- conductive material with a melting point of at least about 300 °C.4637-0022WO0117. The ICP ion source assembly of Claim 16, wherein the envelope comprises any of a ceramic, glass, alumina, fused silica and sapphire.

18. An inductively coupled plasma (ICP) ion source assembly (100) for use in mass cytometry, comprising:an envelope (102) surrounding a plasma zone (104),a conduit (110) extending into the envelope and having a first end (112) adjacent the plasma zone, anda ceramic injector (114) positioned within the conduit and having an outlet (116),wherein outlet of the ceramic injector extends past the first end of the conduit and into the plasma zone such that when a plasma (108) is maintained in the plasma zone the outlet is in contact with the plasma, andwherein the ceramic injector is configured such that it can operate substantially continuously with a sample cell concentration of about 2 M / mL or greater for more than about 15 hours without a substantial decrease in single cell events per second.

19. The ICP ion source assembly of Claim 18, wherein the ceramic injector is configured such that it can operate substantially continuously with a sample cell concentration of about 5 M / mL or greater for more than about 15 hours without a substantial decrease in single cell events per second.

20. The ICP ion source assembly of Claim 18, wherein the ceramic injector outlet has an opening diameter between about 0.4 mm and about 0.8 mm, and the ceramic injector has a lumen (118) in fluidic communication with the outlet, the lumen having a diameter greater than the outlet opening diameter.

21. The ICP ion source assembly of Claim 20, where in the lumen diameter is between about 1 mm and about 10 mm.4637-0022WO0122. The ICP ion source assembly of Claim 20, wherein the lumen diameter directly transitions to the outlet opening diameter at the outlet opening.

23. The ICP ion source assembly of Claim 22, wherein the transition from the lumen diameter to the outlet opening diameter describes a truncated cone with one end of the cone coterminous with the outlet opening.

24. The ICP ion source assembly of Claim 23, wherein the truncated cone has a tapering angle a between about 5 and about 180.

25. The ICP ion source assembly of Claim 23, wherein the truncated cone has a tapering angle a between about 10 and about 100.

26. The ICP ion source assembly of Claim 23, wherein the truncated cone has a tapering angle a between about 20 and about 90.

27. An inductively coupled plasma (ICP) ion source assembly (100) for use in mass cytometry, comprising:an envelope (102) surrounding a plasma zone (104),a conduit (110) extending into the envelope and having a first end (112) adjacent the plasma zone, anda ceramic injector (114) positioned within the conduit and having an outlet (116),wherein outlet of the ceramic injector extends past the first end of the conduit and into the plasma zone such that when a plasma (108) is maintained in the plasma zone the outlet has a temperature in the range between about 350 °C and about 600 °C.

28. The ICP ion source assembly of Claim 27, wherein the ceramic injector is configured such that it can operate substantially continuously with a sample cell concentration of about 2 M / mL or greater for more than about 15 hours without a substantial decrease in single cell events per second.4637-0022WO0129. The ICP ion source assembly of Claim 27, wherein the ceramic injector outlet has an opening diameter between about 0.4 mm and about 0.8 mm, and the ceramic injector has a lumen (118) in fluidic communication with the outlet, the lumen having a diameter greater than the outlet opening diameter.

30. The ICP ion source assembly of Claim 29, where in the lumen diameter is between about 1 mm and about 10 mm.

31. The ICP ion source assembly of Claim 29, wherein the lumen diameter directly transitions to the outlet opening diameter at the outlet opening.

32. The ICP ion source assembly of Claim 31, wherein the transition from the lumen diameter to the outlet opening diameter describes a truncated cone with one end of the cone coterminous with the outlet opening.

33. The ICP ion source assembly of Claim 32, wherein the truncated cone has a tapering angle a between about 5 and about 180.

34. The ICP ion source assembly of Claim 32, wherein the truncated cone has a tapering angle a between about 10 and about 100.

35. The ICP ion source assembly of Claim 32, wherein the truncated cone has a tapering angle a between about 20 and about 90.

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